This invention relates to a device comprising structure where a flexible printed circuit board is connected to another circuit board and a connection auxiliary member for use on connecting them.
Inasmuch as liquid-crystal display devices have characteristics of thin, lightweight, and low power consumption, the liquid crystal display devices have been used in a wide area such as office automation (OA) equipments, audio visual (AV) equipments, portable terminal equipments. The liquid-crystal display device comprises a liquid crystal panel where liquid crystal is sandwiched between opposed two substrates, a backlight for illuminating the liquid crystal panel, and a cabinet for holding and fix them.
The above-mentioned backlight comprises a lot of members such as a lamp of a light source, a flexible printed circuit board connected to the lamp, a lamp holder for holding the lamp, a light guide plate for guiding a lamp beam to an irradiation surface in its entirety, a reflecting sheet for reflecting the lamp beam, and a dispersion sheet for dispersing the lamp beam through the light guide plate. The light source may be a light emitting diode (LED), a cold cathode fluorescent lamp (CCFL), or an external electrode fluorescent lamp (EEFL). In order to obtain a uniform irradiation beam, it is necessary for the backlight to correctly assemble respective members. Therefore, the backlight is normally dealt with as a backlight unit where their members are held and fixed by the cabinet such as a front chassis or a rear chassis.
Under the circumstances, the liquid-crystal display device is assembled by disposing the liquid-crystal panel in the irradiation surface side of the backlight unit, by disposing a circuit board on which a power-supply circuit for lighting the lamp up is formed in a rear surface side of the rear chassis, and by connecting the flexible printed circuit board derived from the cabinet of the backlight unit with a connector mounted on the circuit board.
Japanese Unexamined Patent Application Publication of Tokkai No. 2001-75,116 or JP-A 2001-75116 discloses a LCD device having structure where a main circuit board has an opening part formed at one part thereof and a connector on a rear side of an LCD circuit board and a connector on a rear side of the main circuit board are connected with a flexible flat cable through the opening part.
Japanese Unexamined Patent Application Publication of Tokkai No. Hei 11-327,458 or JP-A 11-327458 discloses a plane display device comprising a display panel and a circuit board for driving the display panel. The display panel has electrode terminals which are connected to the circuit board through flexible cables. The electrode terminals are connected to electrode connectors. The circuit board has board connectors while the flexible cables have printed boards. The board connectors are connected to the printed boards.
Japanese Unexamined Patent Application Publication of Tokkai No. Hei 9-101,536 or JP-A 9-101536 discloses a mounting method for display panel. A liquid crystal panel has a peripheral edge part in which connection terminals are formed. Each connection terminal is electrically connected to one end of a flexible wiring board. A common wiring board is arranged at the rear of the liquid crystal panel. The flexible wiring board is bent and another end of the flexible wiring board is electrically connected to the common wiring board by solder.
Japanese Unexamined Patent Application Publication of Tokkai No. 2006-78,790 or JP-A 2006-78790 discloses a display panel on which an IC chip is mounted. The display panel has a conductive part connected to an electrode of the IC chip. The conductive part is connected to one end of a flexible printed circuit (FPC).
Inasmuch as the flexible printed circuit has flexibility, it is feared that the flexible printed circuit derived from the chassis is in contact with another member to become damaged on transferring or handling the backlight unit.
Therefore, on assembling the backlight unit, in the manner which will later be described in conjunction with FIG. 22, terminal portions of the flexible printed circuits are disposed so as to overlap a circuit board mounted area on the rear chassis and parts except for the vicinity of the terminal portions are fixed on the rear chassis by means of hooks. However, when the circuit board is disposed on the rear chassis in this state, the terminal portions of the flexible printed circuits will be caught between the rear chassis and the circuit board.
Therefore, after the circuit board is disposed, the terminal portions of the flexible printed circuits are pulled out between the rear chassis and the circuit board. It results in occurring redundant working and malfunctions so that the flexible printed circuits receive flaws or are broken. In order to prevent such malfunctions, it is necessary to conduct difficult work so as to lift up the terminal portions of the flexible printed circuits by one hand and to dispose the circuit board by another hand. Accordingly, the workability becomes worse and it results in a malfunction so that the flexible printed circuits are broken by exerting an excess force on the flexible printed circuits.
The above-mentioned problems in connecting the flexible printed circuit are not limited to the backlight unit and occur in any device having a mounting structure where a flexible printed circuit is disposed on a surface of a chassis and a circuit board is disposed so as to overlap a terminal portion of the flexible printed circuit.